This invention generally relates to recording and reproducing apparatus such as magnetooptical recording and reproducing apparatus using a magnetooptical head or the like. More particularly, the present invention relates to a magnetooptical head capable of reducing the diffraction limit of the spot diameter of the laser beam irradiated on a recording medium, and to a recording and reproducing apparatus capable of recording at a higher density by use of the magnetooptical head unit.
Recently, as multimedia have become popular, a magnetooptical recording medium which is able to record and reproduce a large amount of data rapidly and at a higher density has attracted a great deal of public attention. For example, with regard to recording on a magnetooptical recording medium capable of overwrite recording, a laser beam is irradiated on the magnetooptical recording medium, while a magnetic field corresponding to input information is applied to the positions on the medium at which the laser beam has been irradiated. When this magnetooptical recording medium is reproduced, a laser beam weaker than that at the time of recording is applied to the medium, and the polarizing angle of the reflected light from the medium, which has the polarizing angle of the reflected light depending on the recording magnetization direction, is detected so that the information can be reproduced.
As to the head mechanism used in this magnetooptical recording and reproducing apparatus, an optical head 2 and a magnetic head 3 as shown in FIG. 1 have been provided to oppose each other along their center line on both sides of a disk recording medium 1. In this case, since each of the optical head 2 and magnetic head 3 has a large shape and weight, the heads 2, 3 are supported by a support member 7, and moved along the sides of the disk recording medium 1 by the rotation of a screw rotating shaft 4 driven by a drive motor 6, so that the information can be recorded, reproduced or erased. This system has a drawback in that it has a large three-dimensional shape and a large weight. Thus, it is not suitable for small-size, light weight, large-capacity, and high-speed access for recording, reproduction and erasion which the disk recording medium and recording and reproducing apparatus are requested to have. On the other hand, a magnetooptical head mechanism 20 as shown in FIG. 2 is known as the technology for combining the optical head 2 and magnetic head 3 into one unit, thereby reducing the size of the recording and reproducing apparatus. That is, a drive 13 for an object lens 10 of an optical head system 12 and a magnetic head/slider 14 in which a magnetic head coil 21 is provided are integrally combined. The magnetic head/slider 14 has an aperture 43 formed therethrough for focused light 32 of a laser beam 11 emitted from the optical head. The recording and reproducing apparatus using this kind of magnetooptical head is considerably small in its solid volume, but still not satisfactory enough to meet the small-size, light weight, large-capacity, and high-speed access for recording, reproduction and erasion which the disk recording medium and recording and reproducing apparatus of today are requested to have.
In addition, another system is known in which the head is secured to the tip of an arm with its fulcrum positioned around the disk recording medium. The arm is swung in parallel to the surface of the disk recording medium, thereby recording, reproducing or erasing information on or from the disk recording medium. The drive system for moving the optical head in parallel to the surface of the disk recording medium by a swing arm or linear motor is proposed in Japanese Patent Laid-open Gazette No. 5-54457. The system for driving an optical head by a swing arm is also proposed in Japanese Patent Laid-open Gazettes Nos. 8-7309 and 3-203848. Moreover, the construction having a laser beam reflecting surface formed on the magnetic head is disclosed in Japanese Patent Laid-open Gazette No. 3-280233. The problem with this system is that it is not able to achieve the suitable small size and light weight which the recording and reproducing apparatus of today is requested to have. The recording and reproducing drive capable of answering the remarkable demand for small size and high-density recording capability of a magnetooptical recording medium must be more compact, lighter in weight, and have higher-speed access for recording, reproduction and erasion. If the optical head and magnetooptical head are driven by the known swing arm system, the heads will hit the disk recording medium, causing head crash with the result that the head and disk recording medium are broken, or destroyed.
The recording and reproducing drive is required to have a small volume, be as compact as possible, make much faster access for the recording, reproduction and erasing, and have high-performance recording, reproducing and erasing functions capable of reading, recording and erasing more highly fine information signal pits, magnetic domains or domain signals on/from the recording medium than in the prior art. In addition, the head unit should be light in weight, and as a result the weight of the whole recording and reproducing drive must be light. In this connection, recording media such as magnetooptical disks are also required to have smaller diameters, light weights, higher recording capacities capable of recording at higher densities, and higher performance functions to record, reproduce and erase at a higher speed. These features have been gradually developed so far. The important thing for reducing the volume of the recording and reproducing drive is to decrease the thickness of the drive. In order to achieve this object, it is necessary that the record/reproduce head for the access to the magnetooptical disk be chiefly moved in parallel to the recording surface of the magnetooptical disk, and moved as little as possible in the perpendicular direction relative to the recording surface of the magnetooptical disk or reduce the volume to a minimum. Also, in order to make the access of the record/reproduce head to the recording medium more rapid, it is necessary to use a head mechanism capable of quick movement, and to control the record/reproduce head and magnetooptical disk to prevent collision, or crashing with each other.
Accordingly, it is an object of the invention to provide a recording and reproducing drive apparatus capable of recording, reproducing and erasing a large amount of information at high speed on/from a disk-like information recording medium that is able to record information at a high density, and particularly a recording and reproducing drive apparatus having a swing arm of which the tip end has securely mounted thereon an optical head or a magnetooptical head produced by combining an optical head and a magnetic head into a unitary body. The swing arm/head according to the invention is mounted at the fulcrum near the outer periphery of the disk recording medium loaded in the recording and reproducing drive apparatus. Thus, this swing arm/head function to pivotally move around this fulcrum in a fan shape in parallel to the recording surface of the disk recording medium, and to record/reproduce/erase information on/from the disk recording medium. The swing arm/optical head or swing arm/magnetooptical head according to the invention is a head mechanism that has the function to irradiate an extremely fine xe2x80x9claser beam spotxe2x80x9d unit signal or a highly fine xe2x80x9cmagnetic fieldxe2x80x9d unit signal to a small-sized high-density recording disk medium to fast record/reproduce/erase a high-density information signal such as an ultra-fine xe2x80x9cpitxe2x80x9d unit signal or ultra-fine xe2x80x9cmagnetic domain or domainxe2x80x9d unit signal or to fast make information processing for record/reproduce/erase operation on this high-density information signal. The recording and reproducing apparatus of the invention has a swing arm that is formed of at least a head unit, swing arm portions, and an optical beam splitter. In addition, the head unit is securely mounted to the tip end of the swing arm with its swing driving pivot located near the outer periphery of the recording medium loaded in the recording and reproducing apparatus. Also, the head unit is formed of an object lens drive and a laser-beam-permeable member of which the center coincides with the center line of an object lens. The laser-beam-permeable member of the head unit may be formed by a head slider having a head floating function. The recording medium to be loaded in the recording and reproducing apparatus of the invention can be selected from an optical recording medium, a magnetooptical recording medium, a magnetic recording medium for making optical beam tracking, and so on. Particularly, the optical disk recording medium, magnetooptical disk recording medium and magnetic recording medium for making optical beam tracking are suitable for use with the recording and reproducing apparatus of the invention. Of the recording and reproducing apparatus of the invention, the magnetooptical recording and reproducing apparatus has provided therein a swing arm that is formed of at least a head unit, a slider, swing arm portions, and an optical beam splitter. The head unit has a swing driving pivot provided near the outer periphery of the magnetooptical disk loaded in the magnetooptical recording and reproducing apparatus. In addition, the head unit securely mounted on the tip of the arm is formed of an object lens drive, a head slider having a laser-beam-permeable member of which the center coincides with the center line of the object lens, and a magnetic coil. If a solid immersion lens is fixedly provided in the laser-beam-permeable member of which the center coincides with the center line of the object lens of the head unit, such an effect can be obtained as to be able to read, write and erase extremely fine information pits, information magnetic domain signal, information domain signal and so on/from the recording layer of the recording medium. Moreover, the recording and reproducing apparatus of the invention has a swing arm which is formed of at least a head unit, a slider, swing arms and a light beam splitter. This head unit is fixedly mounted on the disk-side tip end of the balance-shaped swing arm having a swing driving pivot provided near the outer periphery of the disk recording medium loaded in the recording and reproducing apparatus. A signal detection unit for the disk recording medium may be securely mounted on the other end of the balance-shaped swing arm.
The swing arm/head according to the invention may be adapted so that the whole arm/head or only the head unit of the swing arm which is mounted at the fulcrum near the outer periphery of the disk recording medium loaded in the recording and reproducing apparatus records/reproduces/erases information on/from the disk recording medium while it is being linearly moved from the fulcrum on the swing arm in parallel to the recording surface of the disk recording medium in substantially the diameter direction of the disk recording medium. This driving means for linearly moving this head is a linear motor.
The swing arm or the head unit mounted on the arm has the function to cause a negative or positive pressure in the air circulated by convection while the disk recording medium is being rotated, thereby floating the head unit itself. The head unit is formed of a head slider with a portion provided to cause the light beam spot to pass therethrough, a magnetic coil or film-shaped magnetic coil, an object lens drive, and a laser beam reflecting mirror. The portion of the head slider for allowing the laser beam to pass therethrough may be an aperture, a transparent ceramic member or a transparent resin material formed in the path. Also, a hemispherical transparent lens or solid immersion lens can be fixedly provided near this laser beam permeable portion.
The swing arm/head or head unit mounted on the arm according to the invention not only makes tracking the information recording area of the disk recording medium by irradiating a laser beam thereon from the optical head and records/reproduces/erases an information signal on/from the area, but also has the function to control the amount of floating of the swing arm and the focusing necessary for the recording/reproducing/erasing of the information signal. In particular controls the object lens drive and prevents the swing arm/head from being crashed.
The magnetooptical head unit of the invention, since the magnetic coil is incorporated in the slider, can be smaller in size than in the prior art. In addition, since the magnetic coil is disposed on the outer periphery of the optical element 101, the distance between the recording medium and the magnetic coil is decreased. Therefore, the current flowing in the magnetic coil can be reduced when it produces a magnetic field. Thus, since the path along which the laser beam is irradiated is not blocked, the laser beam can be effectively irradiated on the recording medium. Since the magnetic coil is located at a position near to the recording medium away from the light-exiting surface of the optical element 101, the magnetic coil is close to the recording medium, thus suppressing the consumption power of the recording and reproducing apparatus using this magnetooptical head unit. The magnetic coil should be made of a film-like coil. Since the magnetic coil is constructed with a film-shaped coil, the distance between the recording medium and the magnetic coil can be reduced. Moreover, if the inner diameter of the magnetic coil is reduced to be smaller than the outer diameter of the optical element 101, the magnetic coil can apply a more stable magnetic field to the recording medium.
The magnetic core should be made of a magnetic material that is permeable to light. Thus, since the laser beam irradiated toward the recording medium is not blocked, the laser beam can be effectively irradiated on the recording medium. The magnetic material for the core may be, for example, transparent ferrite. In the magnetooptical head unit of the invention, at least a part of the optical element should be made of a laser-beam-permeable magnetic material. By employing this construction, it is possible to reduce the number of parts for use in constructing the magnetooptical head unit, and hence miniaturize the magnetooptical head unit. In addition, the laser-beam-permeable magnetic material can be disposed only near the central portion of the optical element perpendicular to the laser-beam-exiting surface of the optical element, thereby increasing the precision with which the external magnetic field is positioned.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.